/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.solr.update.processor;

import static org.apache.solr.update.processor.FieldMutatingUpdateProcessor.SELECT_NO_FIELDS;
import static org.apache.solr.update.processor.FieldValueMutatingUpdateProcessor.valueMutator;

import org.apache.solr.common.SolrException;
import org.apache.solr.common.SolrException.ErrorCode;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.core.SolrCore;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;
import org.apache.solr.update.processor.FieldMutatingUpdateProcessor.FieldNameSelector;

/**
 * Truncates any CharSequence values found in fields matching the specified conditions to a maximum
 * character length.
 *
 * <p>By default this processor matches no fields
 *
 * <p>For example, with the configuration listed below any documents containing a String in any
 * field declared in the schema using <code>StrField</code> will be truncated to no more then 100
 * characters
 *
 * <pre class="prettyprint">
 * &lt;processor class="solr.TruncateFieldUpdateProcessorFactory"&gt;
 *   &lt;str name="typeClass"&gt;solr.StrField&lt;/str&gt;
 *   &lt;int name="maxLength"&gt;100&lt;/int&gt;
 * &lt;/processor&gt;</pre>
 *
 * @since 4.0.0
 */
public final class TruncateFieldUpdateProcessorFactory extends FieldMutatingUpdateProcessorFactory {

  private static final String MAX_LENGTH_PARAM = "maxLength";

  private int maxLength = 0;

  @Override
  public void init(NamedList<?> args) {

    Object lengthParam = args.remove(MAX_LENGTH_PARAM);
    if (null == lengthParam) {
      throw new SolrException(
          ErrorCode.SERVER_ERROR, "Missing required init parameter: " + MAX_LENGTH_PARAM);
    }
    if (!(lengthParam instanceof Number)) {
      throw new SolrException(
          ErrorCode.SERVER_ERROR,
          "Init param "
              + MAX_LENGTH_PARAM
              + "must be a number; found: \""
              + lengthParam.toString());
    }
    maxLength = ((Number) lengthParam).intValue();
    if (maxLength < 0) {
      throw new SolrException(
          ErrorCode.SERVER_ERROR,
          "Init param " + MAX_LENGTH_PARAM + "must be >= 0; found: " + maxLength);
    }

    super.init(args);
  }

  @Override
  public FieldNameSelector getDefaultSelector(final SolrCore core) {
    return SELECT_NO_FIELDS;
  }

  @Override
  public UpdateRequestProcessor getInstance(
      SolrQueryRequest req, SolrQueryResponse rsp, UpdateRequestProcessor next) {
    return valueMutator(
        getSelector(),
        next,
        src -> {
          if (src instanceof CharSequence s) {
            if (maxLength < s.length()) {
              return s.subSequence(0, maxLength);
            }
          }
          return src;
        });
  }
}
